The present invention relates to a safety valve for a compressed gas reservoir, with an exhaust duct which is connected to the compressed gas reservoir, and a sealing element which is arranged to move within the exhaust duct and which opens the exhaust duct to the outside depending on the operating phase.
A safety valve of this general type is disclosed in German patent document DE 10 2006 020 388 A1. Furthermore, a safety valve for a compressed gas reservoir is known from European patent document EP 1 655 533 A1, in which the sealing element is formed with cross-sectional surfaces of different sizes at the ends, and the sealing element is furthermore pre-tensioned with a spring and can be moved back and forth axially.
An exhaust process, in particular the exhaust of hydrogen contained in the compressed gas reservoir, can take place only in a very insufficient manner with the known safety valves. In particular, the requirement of a constant mass flow during the exhaust process is satisfied only in a very unreliable manner.
One object of the present invention, therefore is to provide a safety valve for a compressed gas reservoir, in which a constant mass flow can be exhausted more reliably during an exhaust process.
This and other objects and advantages are achieved by the safety valve for a compressed gas reservoir according to the invention, which comprises an exhaust duct connected to the compressed gas reservoir. A sealing element, which is arranged to move within the exhaust duct and opens it to the outside depending on the operating phase, has a greater cross-sectional area on the side facing away from the compressed gas reservoir than on the side facing the compressed gas reservoir. The exhaust duct is formed with a constriction on the side of the sealing element facing away from the compressed reservoir. With such a safety valve, the exhaust of a constant mass flow during an exhaust process can be achieved in a considerably more precise manner and virtually without fluctuations.
The constriction is preferably formed in such a manner that the cross section of the exhaust duct is greater at the constriction than before and behind it. The constriction or the narrow point is thus designed in such a manner that a widening of the flow cross section is given again in the flow direction on both sides of the constriction. This contributes to keeping the mass flow to be exhausted constant in a particularly preferred manner.
The constriction is preferably formed in the exhaust direction of the medium and thus in the flow-out direction of the medium behind the sealing element in the exhaust duct. This enables a particularly suitable application locally and functionally with regard to the mass flow to be exhausted in a constant manner.
The exhaust duct is in particular formed with a section in the exhaust direction of the medium in front of the constriction, which section has a flow cross section that is smaller than a flow cross section of the exhaust duct in front or behind this section. Narrow points are thus formed in the exhaust duct at both sides of the safety valve, whereby the adjustment of a highly precise constant mass flow during an exhaust process can be achieved in a particularly advantageous manner.
This section is preferably formed as a bore in the sealing element, in particular in the end part of the sealing element facing the compressed gas reservoir.
The end portion of the sealing element preferably has the smaller cross-sectional surface of the sealing element, which is larger than the surface of the flow cross section of the section of the exhaust duct.
The sealing element is preferably a piston that can be displaced in the axial direction.
The sealing element is preferably held in its starting position with a sealing and locking element lying on the inside. The starting position is defined if an exhaust process is not carried out and the sealing element is thus held in this starting in a positionally stable manner. The sealing and locking element has the function of sealing the exhaust duct on the one hand, if an exhaust process is not carried out, and has the locking of the sealing element in this starting position, if an exhaust process is not carried out.
The sealing and locking element is filled with a liquid in a advantageous manner. The activation of the sealing and locking element can be achieved by this design in a particularly simple manner, and with little effort in safety-critical situations, so that it is destroyed.
It can in particular be provided in this connection that the sealing and locking element loses its sealing and locking function in dependence on a temperature charge, in particular the temperature charge of the liquid. It is hereby provided in particular that the liquid evaporates during heating and expands thereby, which leads to a bursting of the sealing and locking element and the sealing function and the locking function is thus lost, whereby the sealing element can be moved from its starting position.
The sealing and locking element is in particular a cylindrical capsule, in particular of glass or a glass-like material, which is filled with a liquid evaporating at a high temperature. A high temperature in this connection is meant to be such a temperature which can for example be present with safety-critical states in which a fire occurs. The temperature increase of the liquid caused by the fire then leads to the evaporation and the destruction of the sealing and locking element.
The sealing and locking element preferably extends into the interior of the sealing element in its assembly position and abuts a housing wall with a first end projecting from a section of the exhaust duct formed in the sealing element, and abuts a projection of the inner wall, which is formed for reducing the flow cross section of the exhaust duct at the inner wall with a second end arranged in the sealing element. This is a particularly advantageous, and with regard to the function, a particularly suitable positioning. Furthermore, this specific position of the sealing and locking element can be generated and kept in a simple manner by the specific formation of the exhaust duct in the sealing element and the positioning of the sealing element.
The sealing and locking element is preferably arranged in the exhaust direction of the medium to be exhausted between the constriction and the section of the exhaust duct with a reduced cross section.
The sealing element is in particular coupled to a pre-tensioning element, such as a spring, for the movement guide during the exhaust process. The movement of the sealing element can thus be adjusted continuously and in a very exact manner in dependence on the formed pressure states, so that undesired large fluctuations of the mass flow to be exhausted can also be changed in this regard.
The compressed gas reservoir is in particular formed for receiving fuel, in particular hydrogen or gas containing hydrogen, of a fuel cell system
Safety problems can be provided especially in the case of fire by means of the suggested safety valve, as it can be prevented that very high mass flows exit from the exhaust line. High fluctuations of the medium to be exhausted can furthermore also be prevented. This is in particular achieved by means of a mechanical valve, in which the mass flow to be exhausted during the exhaust process can be kept constant independently of the primary pressure.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.